Thermostatically-actuated electric switch



June 10, 1930. E. M CABE I THERMOSTATICALLY ACTUATED ELECTRIC SWITCH INVENTOR ATTORNEY June 10, 1930. l. E. M CABE THERMOSTATICALLY ACTUATED ELECTRIC SWITCH Filed Oct. 10, I 1928 2 Sheets-Sheet INVENTOR E'. M? C'Afif TTORNEY v oithe Patented 10, 1930 UNITED STATES m n McCABE, or cnrcneo, rumors THEBMOSTATICALLY-ACTUATED ELECTRIC SWITCH Application filed October 10, 1928. Serial No. 811,486.

This invention relates to thermostatically actuated electric switches and more particularly to a switch of this character so constructed that the expansion or contraction of the thermostatically actuated member will upon movement in either direction, irrespective of its condition, immediately throw the switch andthen may expand or contract to a greater degree freely and irrespectively of osition of the switch mechanism. ith these and other objects in view, reference is made to the accom )a-nying sheet of drawing illustrating a re erred embodiment of this invention wit the understanding that minor detail changes may be made without departing from the scope thereof.

In the drawings: Figure 1 is a view in side elevation of an embodiment of this invention as applied to a stack control switch employed in an electrically operated domestic liquid fuel heatin system, with parts broken away.

igure 2 is a view 'in' front elevation of Figure 1.

Figure 3 is a fragmentary detail View with the switch carrier plate removed, indicated in dot and dash l nes, illustrating the normal relation of the parts assumed when the actuating member has reached the normal limit of its travel.

Figure 4 is a similar view illustrating the relation of the parts assumed as the actuating member continues movement in the same direction.

Figure 5 is a similar view illustrating the normal relation of the parts when the actuating member has reached the normal limit of its travel in the reverse direction.

Figure 6 is a similar view illustrating the 4 relation of the parts assumed as the actuating member continues movement in that direction.

Figure 7 is a detailed fra in perspective of the assembled actuating parts.

mentary view Figure 8 is a similar view of the switch carrier plate.

In electrically operated domestic heating plants an electric motor is employed to supply the fuel to the furnace or heater as required and in such systems a safety device is customarily placed in the motor circuit, or arran 'ed to control the motor circuit,- which safety device is in the form of a thermostatically actuated electric switch responsive to combustion condition. This type of switch is shown and described herein to illustrate one embodiment of this invention,

bi-metallic metal adapted to be inserted and held within the stack of an oil burning furnace in the usual manner. Since the so called stack safety for controlling the motor circuit of a liquid fuel heating system is an old and well known commercial device, no further description is deemed necessary beyond the statement that one end of the thermostatic coil 3 is held stationary and the other secured to the free end of the shaft is rotated first in one direction and then in the reverse direction.

The end of the shaft 2 enters within the casing 1 and non-rotatably mounts a disc or wheel 4, which may be keyed to the shaft in any preferred manner, and the end of the shaft also rotatably mounts a switch carrier plate 5 which maybe held against longitudinal movement therein in any desired manner so that the rotation of the flat surfaces of the disc or wheel 4 and carrier plate remain parallel. The carrier late 'oreferabl is of such dimensions that one of its upper corners 6 engages the side walls of the casadapted to engage and travel. over the circumference of the disc or wheel is mounted between the plates 9 and is maintained in contact therewith by the weight of the plates 5 9 which extend beyond.

it is preferable to construct this carrier plate 5 as shown in Figure 1, having the upper right hand portion 6 above the shaft 2 extended to engage casing wall to limit tion that direction, with the bod ne plate extended below to the left i 2 so that when free to rotate about 2 plate will normally swing about shaft 2 until the portion 5 engages the cas- IV.

The plates 9 are somewhat triangular shaped and the longest side or base arranged at the bottom and the shaft openin arranged substantially above the center t ereof. The plates are preferably held together in spaced apart relation by spacing members 9 secured thereto and by being pivoted to the carrier plate 5 below and at one side of the shaft 2 and being cut awa about the shaft, the plates are capable o a certain amount of free movement about the pivot 7.

The disc or wheel 4- is provided with a series of peripherial teeth so that the weight of the portion of the plates 9 on the other side of the shaft 2 will normally hold the roller in contact with the body of disc or wheel between the apices of two adjacent teeth, and upon rotation of the shaft 2 in one direction the disc or wheel 4 will rotate therewith and roller 8 carried between the plates 9 will through the contacting relation to the toothed surface of the disc and connection of the pivot 7 to the carrier plate 5 impart a rotation movement to said late in the same direction as the rotation o the shaft until the corner 6 of the plate 5 engages the side wall of the casing and when this occurs the plate will remain stationary and continued rotation of the shaft 2 in the same direction forces the roller 8 outward against the weight of plates 9 causing it ,to continue to ride over the apices of the toothed surface of the disc as long as rotation in that direction continues and when rotation of the shaft 2 ceases the roller contact will maintain the plate stationar but immediately upon reverse rotation o the shaft the roller connection will impart a reverse ro- 1,7e2,1ss

tation to the plate 5 .until the under side 10 of the plates 9 engage a stop 11 upon the casing wall and continued reverse rotation of the shaft 2 will maintain the carrier plate 5 stationary as long as the toothed surface of the disc continues to pass below the roller 8.

The switch carrier plate 5 is provided with plate 5 below the shaft 2 in such a position that if plate 5 is free to rotate about shaft 2 the weight thereof will swing the plate to tilt the switch to open the circuit therethrough. Should the safety feature depend upon the closing of circuit, the switch 12 will be attached to plate 5 in reverse to the position shown in Figure l. The pivotal connection of the plates 9, with the enlarged v openings about shaft 2, to plate 5 allows of any desired adjustment for the normal position of switch 12 to be made by hand when the instrument is installed. The shape of plates 9 and 5 with their main bodies below the shaft 2 and their pivotal connection to each other below and to the left of shaft 2 normally tends to rotate the plate 5 in the direction to bring its extension 6 in contact with the side of the casing wall, as shown in Figure 1. Therefore, should for any reason the shaft become detached from the thermostatic coil 3, such as the heat to which the coil is subjected during the employment of the device burn to consume the coil, the shaft 2 is free to rotate and allow plate 5 with its gravity connection with disc 4 to assume its normal position.

The above described weight actuated or gravity connection between the shaft 2 and switch carrier plate 12 roduces a positive switch operating mechamsm actuated by the expansion and contraction of the thermal 7.

element 3, the sensitiveness of which depends upon the number and character of the teeth upon the circumferential surface of the disc 4, and at the same time allows an unrestrained amount of expansion and' contraction of the thermal element 3 to rotate the shaft 2 beyond that required to tilt the mercury tube switch to open and 'c metal constantly subjected to changesin temperature to which it is responsive- Likewise, the efliciency of this device is obvious as well as its reater length of the operating life bothv of which characteristics are desirable and indeed most necessar to a safety device of this general type. it is also obvious that this invention can readily be applied to an other'type of thermostatically operate electric switches, suchas a rooin thermostat for controllin an electric circuit for operating dampers a coal furnace or the motor of a liquid fuel burning system or similar devices in" which the t ermostatic element in expanding and contracting causes the rotation of a shaft, sleeve or other member to actuate a mercury tube switch. It is to be noted that in this device I that the absence of springs or other devices which will deteriorate with age and use is conspicuous, and should the heat to which the thermostatic element is subjected be sufficient to burn or consume the same the gravity actuated roller will automatically return the switch to the oil position on account of the excess weight upon the roller when the switch is in the closed position.

What Iclaim is: i

1. A temperature responsive electric switch having a temperature responsive ele ment the movement of which is adapted to actuate a switch operating mechanism including a rotatable member actuated by said element, a rotatable switch v carrier mounted thereon, a mercury tube switch mounted upon said carrier, said rotatable member provided with a toothed track, said switch carrier pivotally connected to a gravity actuated member, said member mounting a roller adapted to travel over said track, and said gravity actuated member acting upon said roller to hold it in contact with said track, whereby upon rotation of the rotatablemember 1n either direction im arts a rotation movement to the carrier p ate:

2. A temperature responsive electric switch having a temperature responsive element the movement of which is adapted to actuate a switch operating mechanism including a rotatable member actuated by said element, a rotatable switch carrier mounted thereon, a mercury tube switch mounted upon-said carrier, said rotatable member provided with a toothed track, said switch carrier pivotally connected to a gravity actuated member, said member mounting a roller adapted to travel over said track, said gravity actuated member acting upon said roller to hold itin contact with said track, whereby upon rotation of the rotatable member in either direction imparts a rotation movement to the carrier plate, means' for limiting the rotation of the carrier plate, said roller connection allowing further rota tion movement of the rotatable member after the movement of the carrier plate has reached its limit.

3, In a device of the character described, a casing, an expansible and contractable element mounted thereon, a shaft rotatably mounted in the casing, adapted to be rotated in one direction as said member expands and in the reverse direction as said member contracts, a disc ri idly secured to said shaft having a toothef track about its periphery, a pivoted switch carrier plate rotatably mounted upon said shaft avinga projection adapted to engage the casing to limit its rotation in one direction, an electric mercur tube switch mounted u on said plate, a roiler carrier plate pivotal connected tosaid plate, a roller mounte adjacent said roller carrier late pivot to be reof the track, theceived between the teet weight on the other extremity of the roller carrier plate, adapted to normally position the roller between teeth of the track, whereby rotation of the shaft in one direction initially rotates the carrier plate in the same direction and u on the plate en a 'ng the casing continue rotation of the s a t in the same direction causes the undulate track to travel under the roller and initial movesaid carrier plate, a roller mounted on said support adapted to travel over said track, and an expansible and contractible member adapted to impart movement to said movable member.

5. A temperature responsive electric switch operating mechanism including amercury tube e ectric switch, a movable member, a toothed track thereon, a pivoted carrier plate for the mercury tube rotatably mounted upon the movable member, a gravity actuated support pivotally connected to said carrier plate, a roller mounted thereon adapted to travel over said track, and an exansible and contractible memberadapted to impart movement to said movable member, means for limiting the rotation of the carrier plate, said roller connection allowing further rotative movement of the rotatable member after the movement of the carrier plate has reached its limit.

6. A temperature responsive electric switch operating mechanism including a mercurytube switch, a movable member, a toothed track thereon, a pivoted carrier plate for the mercur tube rotatably mounted upon the movab e member, a gravity actuated support, pivotally connected to said carrier plate, means thereon engaging said electric teothed track, and an e ansible and contractible member adapte to impart movement to said rotatable member, means for limiting the rotation of the carrier plate,

said connecting means allowing further rotative movement of the rotatable member after the movement of the carrier plate has reached its limit said gravity actuated support returning the switch to open position upon the consumption of the ex ansible member by the heat to which it is suidgcted. IRA E. McC E. 

